%%a 是什么意思？ （批）
What does %%a mean? (Batch)
%%a 是什么意思？
我了解上下文，但不知道如何使用它。
例如：
FOR %%a in (%HELP%) DO echo I don't Know what it means
%%a 指的是您的 for 循环将写入的变量的名称。
引自for /?:
FOR %variable IN (set) DO command [command-parameters]
%variable Specifies a single letter replaceable parameter.
(set) Specifies a set of one or more files. Wildcards may be used.
command Specifies the command to carry out for each file.
command-parameters
Specifies parameters or switches for the specified command.
To use the FOR command in a batch program, specify %%variable instead
of %variable. Variable names are case sensitive, so %i is different
from %I.
示例 1：
for %%a in (A B C D E) do Echo %%a
生产
A
B
C
D
E
示例 2：
for %%a in (A B C) do (for %%b in (1 2 3) do Echo %%a:%%b)
生产
A:1
A:2
A:3
B:1
B:2
B:3
C:1
C:2
C:3
%%a 是什么意思？
我了解上下文，但不知道如何使用它。
例如：
FOR %%a in (%HELP%) DO echo I don't Know what it means
%%a 指的是您的 for 循环将写入的变量的名称。
引自for /?:
FOR %variable IN (set) DO command [command-parameters]
%variable Specifies a single letter replaceable parameter.
(set) Specifies a set of one or more files. Wildcards may be used.
command Specifies the command to carry out for each file.
command-parameters
Specifies parameters or switches for the specified command.
To use the FOR command in a batch program, specify %%variable instead
of %variable. Variable names are case sensitive, so %i is different
from %I.
示例 1：
for %%a in (A B C D E) do Echo %%a
生产
A
B
C
D
E
示例 2：
for %%a in (A B C) do (for %%b in (1 2 3) do Echo %%a:%%b)
生产
A:1
A:2
A:3
B:1
B:2
B:3
C:1
C:2
C:3